A274044 Squarefree numbers that are the sum of two squares in more than one way.

65, 85, 130, 145, 170, 185, 205, 221, 265, 290, 305, 365, 370, 377, 410, 442, 445, 481, 485, 493, 505, 530, 533, 545, 565, 610, 629, 685, 689, 697, 730, 745, 754, 785, 793, 865, 890, 901, 905, 949, 962, 965, 970, 985, 986, 1010, 1037, 1066, 1073, 1090, 1105, 1130, 1145

Offset: 1

Author

Altug Alkan, Jun 07 2016

Keywords

• nonn

Comments

Squarefree numbers that are the sum of two nonzero squares in more than one way.

Examples

			65 is a term because 65 = 5*13 = 1^2 + 8^2 = 4^2 + 7^2.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005117, A007692, A020893.

Programs

PARI

isA007692(n) = {nb = 0; lim = sqrtint(n); for (x=1, lim, if ((n-x^2 >= x^2) && issquare(n-x^2), nb++); ); nb >= 2; }
lista(nn) = for(n=1, nn, if(isA007692(n) && issquarefree(n), print1(n, ", ")));

Formula

A005117 INTERSECT A007692. - R. J. Mathar, Feb 01 2017